In the manufacture of various products from fluid mediums containing essentially particles of two substantially different sizes in suspension, the desired physical properties of such products often depend upon the relative concentrations or proportions of the different size particles. For example, the physical and chemical properties of some latex products depend upon an optimum distribution of two groups of different diameter particles. Thus, the manufacture of one latex product having the desired characteristics will require the maintenance of one ratio between the smaller and the larger particles, whereas the manufacture of another latex product having different characteristics will require the maintenance of a quite different ratio between the larger and smaller particles. To produce products having the desired characteristics, therefore, it is necessary to determine the relative concentrations of the large and small particles.
One reliable technique currently in use for the determination of particle size distribution in suspensions involves the analysis of a suspension by hydrodynamic chromatography (HDC). Although the use of HDC in analyzing a suspension yields accurate, reliable data, the HDC apparatus is of such sophistication that its proper operation requires the services of a chemist or engineer. Further, HDC apparatus reveals considerably more information about a suspension than is required merely to determine the relative concentrations of two particle sizes. Consequently, the use of HDC apparatus for concentration analysis is not the most efficient use of such apparatus.
The analysis of a suspension using HDC apparatus often requires as much as twenty minutes' time to complete. Some production processes, however, require a more rapid method of analysis for process control. Further, it often occurs that HDC apparatus or personnel capable of operating it may not be available at the time an analysis of a suspension is desirable. As a consequence, it is not uncommon for the analysis of a suspension to be completed only after the process has been completed. In some instances, therefore, a finished product may not conform to specifications and must be discarded.
An object of the present invention is to provide a method of analyzing a fluid medium to determine the relative concentration of relatively large and relatively small particles in suspension in such medium and which is simple to perform, requires only a short time to complete, and utilizes relatively inexpensive equipment.